/*

    ......... 2015 Ivan Mahonin

    This program is free software: you can redistribute it and/or modify

    it under the terms of the GNU General Public License as published by

    the Free Software Foundation, either version 3 of the License, or

    (at your option) any later version.

    This program is distributed in the hope that it will be useful,

    but WITHOUT ANY WARRANTY; without even the implied warranty of

    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License

    along with this program.  If not, see <http://www.gnu.org/licenses/>.

*/

#include <cassert>

#include <iostream>

#include "shaders.h"

using namespace std;

Shaders::Shaders():

	simple_vertex_id(),

	simpleProgramId(),

	color_fragment_id(),

	colorProgramId(),

	colorUniform()

{

	// simple

	const char *simpleVertexSource =

		"in vec2 position;\n"

		"void main() { gl_Position = vec4(position, 0.0, 1.0); }\n";

	simple_vertex_id = glCreateShader(GL_VERTEX_SHADER);

	glShaderSource(simple_vertex_id, 1, &simpleVertexSource, NULL);

	glCompileShader(simple_vertex_id);

	check_shader(simple_vertex_id, simpleVertexSource);

	simpleProgramId = glCreateProgram();

	glAttachShader(simpleProgramId, simple_vertex_id);

	glBindAttribLocation(simpleProgramId, 0, "position");

	glLinkProgram(simpleProgramId);

	check_program(simpleProgramId, "simple");

	// color

	const char *colorFragmentSource =

		"uniform vec4 color;\n"

		//"out vec4 colorOut;\n"

		"void main() { gl_FragColor = color; }\n";

	color_fragment_id = glCreateShader(GL_FRAGMENT_SHADER);

	glShaderSource(color_fragment_id, 1, &colorFragmentSource, NULL);

	glCompileShader(color_fragment_id);

	check_shader(color_fragment_id, colorFragmentSource);

	colorProgramId = glCreateProgram();

	glAttachShader(colorProgramId, simple_vertex_id);

	glAttachShader(colorProgramId, color_fragment_id);

	glBindAttribLocation(colorProgramId, 0, "position");

	//glBindFragDataLocation(color_program_id, 0, "colorOut");

	glLinkProgram(colorProgramId);

	check_program(colorProgramId, "color");

	colorUniform = glGetUniformLocation(colorProgramId, "color");

}

Shaders::~Shaders() {

	glUseProgram(0);

	glDeleteProgram(colorProgramId);

	glDeleteProgram(simpleProgramId);

	glDeleteShader(color_fragment_id);

	glDeleteShader(simple_vertex_id);

}

void Shaders::check_shader(GLuint id, const char *src) {

	GLint compileStatus = 0;

	glGetShaderiv(id, GL_COMPILE_STATUS, &compileStatus);

	if (!compileStatus) {

		GLint infoLogLength = 0;

		glGetShaderiv(id, GL_INFO_LOG_LENGTH, &infoLogLength);

		std::string infoLog;

		infoLog.resize(infoLogLength);

		glGetShaderInfoLog(id, infoLog.size(), &infoLogLength, &infoLog[0]);

		infoLog.resize(infoLogLength);

		cout << "~~~~~~~~~~~~~~~~~~~~~~~~~~~" << endl

			 << "cannot compile shader:" << endl

			 << "~~~~~~source~~~~~~~~~~~~~~~" << endl

			 << src << endl

			 << "~~~~~~log~~~~~~~~~~~~~~~~~~" << endl

			 << infoLog << endl

			 << "~~~~~~~~~~~~~~~~~~~~~~~~~~~" << endl;

	}

}

void Shaders::check_program(GLuint id, const char *name) {

 	GLint linkStatus = 0;

	glGetProgramiv(id, GL_LINK_STATUS, &linkStatus);

	if (!linkStatus) {

		GLint infoLogLength = 0;

		glGetProgramiv(id, GL_INFO_LOG_LENGTH, &infoLogLength);

		std::string infoLog;

		infoLog.resize(infoLogLength);

		glGetProgramInfoLog(id, infoLog.size(), &infoLogLength, &infoLog[0]);

		infoLog.resize(infoLogLength);

		cout << "~~~~~~~~~~~~~~~~~~~~~~~~~~~" << endl

			 << "cannot link program " << name <<  ":" << endl

			 << "~~~~~~name~~~~~~~~~~~~~~~~~" << endl

			 << name << endl

			 << "~~~~~~log~~~~~~~~~~~~~~~~~~" << endl

			 << infoLog << endl

			 << "~~~~~~~~~~~~~~~~~~~~~~~~~~~" << endl;

	}

	glValidateProgram(id);

	GLint validateStatus = 0;

	glGetProgramiv(id, GL_VALIDATE_STATUS, &validateStatus);

	if (!validateStatus) {

		GLint infoLogLength = 0;

		glGetProgramiv(id, GL_INFO_LOG_LENGTH, &infoLogLength);

		std::string infoLog;

		infoLog.resize(infoLogLength);

		glGetProgramInfoLog(id, infoLog.size(), &infoLogLength, &infoLog[0]);

		infoLog.resize(infoLogLength);

		cout << "~~~~~~~~~~~~~~~~~~~~~~~~~~~" << endl

			 << "program not validated " << name <<  ":" << endl

			 << "~~~~~~name~~~~~~~~~~~~~~~~~" << endl

			 << name << endl

			 << "~~~~~~log~~~~~~~~~~~~~~~~~~" << endl

			 << infoLog << endl

			 << "~~~~~~~~~~~~~~~~~~~~~~~~~~~" << endl;

	}

}

void Shaders::simple() {

	glUseProgram(simpleProgramId);

}

void Shaders::color(const Color &c) {

	glUseProgram(colorProgramId);

	glUniform4fv(colorUniform, 1, c.channels);

}